Cell-balancing method and battery management system performing the same

ABSTRACT

A battery management system may include a plurality of balancing resistors respectively forming balancing discharging paths of cells connected in series to each other, a plurality of balancing switches respectively connected between the cells and the balancing resistors, and configured to control cell-balancing of each of the cells, a voltage-detecting circuit for detecting respective cell voltages of the cells, and a battery controller for acquiring respective balancing capacities of the cells based on the cell voltages, for obtaining duty cycles of the balancing switches according to the balancing capacities, and for scaling the duty cycles of the balancing switches according to a sum of duty cycles of two adjacent cells from among the cells.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to, and the benefit of, Korean PatentApplication No. 10-2018-0026458 filed in the Korean IntellectualProperty Office on Mar. 6, 2018, the entire contents of which areincorporated herein by reference.

BACKGROUND 1. Field

Embodiments disclosed herein relate to a cell-balancing method and abattery management system for performing the same.

2. Description of the Related Art

Recently, according to strengthening of environmental regulationsincluding CO2 regulations, interest in environmentally-friendly vehicleshas been increasing. Accordingly, vehicle companies have been activelyresearching and developing pure electrical vehicles and hydrogenvehicles, as well as hybrid and plug-in hybrid vehicles.

A high-voltage battery for storing electrical energy obtained fromvarious energy sources is applied to the environmentally-friendlyvehicles. The high-voltage battery includes a plurality of cells coupledin series or coupled in parallel to provide high-voltage electricalenergy. The high-voltage battery includes a battery management system(BMS) for protecting the battery when the battery improperly works bycontinuously or regularly detecting a voltage, a temperature, and acharging and discharging current of respective cells. A cell-balancingfunction for compensating an inter-cell deviation by monitoring statesof the cells is one of major functions of the battery management system.

The cell-balancing may be classified as a passive type or an activetype.

The passive cell-balancing method is a method of balancing a cell havinglarge capacity with a cell having small capacity by discharging the cellcharges having large capacity. The passive cell-balancing method uses asimple control method or a simple control circuit, but power generatedby a discharging is consumed through heat, so radiation of heat becomesan important issue. The active cell-balancing method is a method forbalancing capacities of cells by moving charges to a cell having smallcapacity from a cell having large capacity. The active cell-balancingmethod consumes less power than the passive type to thus provide betterefficiency, but its control is complicated, and it generally uses morecomponents to configure a cell-balancing control circuit.

In the passive cell-balancing method, a discharging path of each cell isconstituted by a resistor (balancing resistor) for determining adischarging current, and a balancing switch. In the case of using thepassive cell-balancing method, the required balance capacity may bedifferent for each cell, but the current flowing through the dischargingpath when the balancing switch is turned on is the same. Therefore, whenthe cells that are subject to balancing simultaneously start to bebalanced, the cells that are balancing objects are discharged just afterthe start of balancing, and the discharging of the cells of which thebalancing is finished may be sequentially stopped. For this reason, whena cell-balancing circuit is designed, it may be useful to account forthe radiation of heat in anticipation of power consumption in the worstcondition in which all of the cells are discharged to be simultaneouslybalanced.

Generally, a method for increasing a balancing current may be used so asto reduce the time used to the cell-balancing, but when the balancingcurrent increases, generation of heat caused by power consumption alsoincreases. Increasing heat radiation performance of the substrate mayresult in the increase of a size of the substrate and a material cost.In addition, when the cell-balancing circuit is actually designed, thedischarge current may be designed to an acceptable level to enable theheat radiation performance of the substrate, even when all of the cellsare simultaneously balance-discharged, so there is a limit in increasingthe balancing current for reducing the cell-balancing time.

The above information disclosed in this Background section is only forenhancement of understanding of the background of embodiments of thedisclosure, and therefore it may contain information that does not formthe prior art that is already known in this country to a person ofordinary skill in the art.

SUMMARY

The present disclosure provides a cell-balancing method for reducing abalancing time while maintaining a heat radiation performance of asubstrate, and a battery management system for performing the same.

An embodiment of the present disclosure provides a battery managementsystem including a plurality of balancing resistors respectively formingbalancing discharging paths of cells connected in series to each other,a plurality of balancing switches respectively connected between thecells and the balancing resistors, and configured to controlcell-balancing of each of the cells, a voltage-detecting circuit fordetecting respective cell voltages of the cells, and a batterycontroller for acquiring respective balancing capacities of the cellsbased on the cell voltages, for obtaining duty cycles of the balancingswitches according to the balancing capacities, and for scaling the dutycycles of the balancing switches according to a sum of duty cycles oftwo adjacent cells from among the cells.

The two adjacent cells may partly share a balancing discharging path forcell-balancing.

Balancing switches of the two adjacent cells may be alternately turnedon.

The battery controller may be configured to calculate a sum of dutycycles of combination of two adjacent cells, may be configured tocalculate a scale factor so that a maximum value of the sum of dutycycles is 100%, and may be configured to scale the duty cycles of thebalancing switches using the scale factor.

The battery controller may be configured to set a ratio of respectiveduty cycles of the balancing switches based on a ratio of respectivebalancing capacities of the cells.

The battery management system may further include a battery integratedcircuit for controlling the balancing switches according to the dutycycles of the balancing switches.

Another embodiment of the present disclosure provides a batterymanagement system including a plurality of balancing resistorsrespectively forming balancing discharging paths of cells connected inseries to each other, a plurality of balancing switches respectivelyconnected between the cells and the balancing resistors for controllinga cell-balancing of each of the cells, a voltage-detecting circuit fordetecting cell voltages of the cells, and a battery controller foracquiring balancing capacities of the cells based on the cell voltages,for obtaining duty cycles of the plurality of balancing switchesaccording to the balancing capacities, and for scaling the duty cyclesof the plurality of balancing switches according to a power consumptionupper limit corresponding to a balancing discharging of the cells.

The battery controller may be configured to calculate a total powerconsumption by summing the balancing capacities of the cells, and may beconfigured to scale the duty cycles of the balancing switches when thetotal power consumption is greater than the power consumption upperlimit.

The battery controller may be configured to calculate a current scalefactor based on a ratio of a current upper limit on a substrate on whichthe balancing resistors are mounted to a sum of average balancingcurrents flowing in each of the balancing discharging paths, and may beconfigured to scale the duty cycles of the balancing switches by usingthe current scale factor.

The battery controller may be configured to scale the duty cycles of thebalancing switches according to a current upper limit allowable to asingle balancing discharging path.

The battery controller may be configured to calculate a current scalefactor of each of the balancing switches based on a ratio of a currentupper limit to an average balancing current flowing in each of thebalancing discharging paths, and may be configured to scale the dutycycles of the balancing switches by using the current scale factor.

The battery controller may be configured to scale the duty cycles of thebalancing switches according to a sum of duty cycles between twoadjacent cells from among the cells.

The battery controller may set a ratio of respective duty cycles of thebalancing switches based on a ratio of respective balancing capacitiesof the cells.

Yet another embodiment of the present disclosure provides a batterymanagement system including a plurality of balancing resistorsrespectively forming balancing discharging paths of cells connected inseries to each other, a plurality of balancing switches respectivelyconnected between the cells and the balancing resistors for controllinga cell-balancing of each of the cells, a voltage-detecting circuit fordetecting cell voltages of the cells, a battery controller for acquiringbalancing capacities of the cells based on the cell voltage, and forobtaining duty cycles of the balancing switches according to thebalancing capacities, and a battery integrated circuit for controllingoperation of the balancing switches by using a balancing task, which isrepeatedly executed during an execution cycle that is shorter than abalancing cycle, and which corresponds to the duty cycles, to allow aturn-on state of the balancing switches only during a part of anexecution period of the balancing task.

The battery integrated circuit may be configured to count on-periods, inwhich the balancing switches are turned on by the balancing task withinone balancing cycle, for each of the balancing switches, and may beconfigured to maintain a state of a balancing switch in a turn-off stateuntil the balancing cycle ends wherein a value obtained by countingon-periods corresponds to a duration of a corresponding duty cycle.

The battery controller may set a ratio of respective duty cycles of thebalancing switches based on a ratio of respective balancing capacitiesof the cells.

The battery controller may be configured to scale the duty cycles of thebalancing switches according to a sum of duty cycles between twoadjacent cells from among the cells.

The battery controller may be configured to scale the duty cycles of thebalancing switches according to a power consumption upper limit of thecells.

The battery controller may be configured to scale duty cycles of thebalancing switches according to a current upper limit of a singlebalancing discharging path.

Yet another embodiment of the present disclosure provides acell-balancing method of a battery pack including a plurality of cellsconnected in series to each other, the method including detecting cellvoltages of the cells, acquiring balancing capacities of the cells basedon the cell voltages, acquiring duty cycles of a plurality of balancingswitches for controlling a balancing discharging of the cells based onone or more respective ratios of the balancing capacities of the cells,and controlling the balancing switches based on the duty cycles.

The cell-balancing method may further include scaling the duty cycles ofthe balancing switches according to a sum of duty cycles between twoadjacent cells from among the cells.

The cell-balancing method may further include scaling the duty cycles ofthe balancing switches according to a power consumption upper limit of abalancing discharging of the cells.

The cell-balancing method may further include scaling the duty cycles ofthe balancing switches according to a current upper limit of one ofbalancing discharging paths of the cells.

The controlling may include repeatedly performing a balancing taskhaving an execution cycle that is shorter than a balancing cyclecorresponding to the duty cycle, and allowing a turn-on state of thebalancing switches only during a part of an execution period of thebalancing task, counting periods in which the balancing switches areturned on by the balancing task within one balancing cycle for each ofthe balancing switches, and maintaining a state of a balancing switch ina turn-off state until the balancing cycle ends, wherein a valueobtained by counting periods in which the balancing switches are turnedon by the balancing task satisfies a duration of a corresponding dutycycle.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an example of performing a cell-balancing.

FIG. 2 to FIG. 5 show examples of a battery pack for performing acell-balancing method according to an embodiments of the presentdisclosure.

FIG. 6 shows a cell-balancing method according to a first embodiment ofthe present disclosure.

FIG. 7 and FIG. 8 show examples of balancing capacity and a changingtrend of average balancing current/power when a cell-balancing controlmethod according to a first embodiment of the present disclosure isused.

FIG. 9 shows an example of a related art cell-balancing control timingdiagram.

FIG. 10 shows an example of a cell-balancing control timing diagram whena cell-balancing method according to a first embodiment of the presentdisclosure is applied.

FIG. 11 shows a cell-balancing method according to a second embodimentof the present disclosure.

FIG. 12 and FIG. 13 show a basic concept of a duty scaling in acell-balancing method according to a second embodiment of the presentdisclosure.

FIG. 14 shows a relationship between total balancing capacity of allbalancing channels and a balancing time when a cell-balancing methodaccording to a second embodiment of the present disclosure is applied.

FIG. 15 shows an example of a case in which a duty scaling is applied toa timing diagram of FIG. 10.

FIG. 16 shows a cell-balancing method according to a third embodiment ofthe present disclosure.

FIG. 17 shows a relationship between total balancing capacity of allbalancing channels and a balancing time when a cell-balancing methodaccording to a third embodiment of the present disclosure is applied.

FIG. 18 shows a cell-balancing method according to a fourth embodimentof the present disclosure.

FIG. 19 shows a relationship between an average balancing current ofbalancing channels and balancing resistance total power when acell-balancing method according to a fourth embodiment of the presentdisclosure is applied.

FIG. 20 shows a cell-balancing method according to a fifth embodiment ofthe present disclosure, showing a case of performing a cell-balancing ina key-on state.

FIG. 21 shows a cell-balancing control circuit for performing acell-balancing method according to a fourth embodiment of the presentdisclosure.

FIG. 22 shows a chart of a cell-balancing control timing diagram of acell-balancing control circuit shown in FIG. 21.

FIG. 23 shows a balancing control timing diagram using a cell-balancingcontrol circuit shown in FIG. 21.

FIG. 24 shows another example of a cell-balancing control circuit forperforming a cell-balancing method according to a fourth embodiment ofthe present disclosure.

FIG. 25 shows a balancing control timing diagram using a cell-balancingcontrol circuit of FIG. 24.

FIG. 26 shows another example of a cell-balancing control circuit forperforming a cell-balancing method according to a fourth embodiment ofthe present disclosure.

FIG. 27 shows a balancing control timing diagram using a cell-balancingcontrol circuit of FIG. 26.

DETAILED DESCRIPTION

Features of the inventive concept and methods of accomplishing the samemay be understood more readily by reference to the detailed descriptionof embodiments and the accompanying drawings. Hereinafter, embodimentswill be described in more detail with reference to the accompanyingdrawings. The described embodiments, however, may be embodied in variousdifferent forms, and should not be construed as being limited to onlythe illustrated embodiments herein. Rather, these embodiments areprovided as examples so that this disclosure will be thorough andcomplete, and will fully convey the aspects and features of the presentinventive concept to those skilled in the art. Accordingly, processes,elements, and techniques that are not necessary to those having ordinaryskill in the art for a complete understanding of the aspects andfeatures of the present inventive concept may not be described. Unlessotherwise noted, like reference numerals denote like elements throughoutthe attached drawings and the written description, and thus,descriptions thereof will not be repeated. Further, parts not related tothe description of the embodiments might not be shown to make thedescription clear. In the drawings, the relative sizes of elements,layers, and regions may be exaggerated for clarity.

Various embodiments are described herein with reference to sectionalillustrations that are schematic illustrations of embodiments and/orintermediate structures. As such, variations from the shapes of theillustrations as a result, for example, of manufacturing techniquesand/or tolerances, are to be expected. Further, specific structural orfunctional descriptions disclosed herein are merely illustrative for thepurpose of describing embodiments according to the concept of thepresent disclosure. Thus, embodiments disclosed herein should not beconstrued as limited to the particular illustrated shapes of regions,but are to include deviations in shapes that result from, for instance,manufacturing. For example, an implanted region illustrated as arectangle will, typically, have rounded or curved features and/or agradient of implant concentration at its edges rather than a binarychange from implanted to non-implanted region. Likewise, a buried regionformed by implantation may result in some implantation in the regionbetween the buried region and the surface through which the implantationtakes place. Thus, the regions illustrated in the drawings are schematicin nature and their shapes are not intended to illustrate the actualshape of a region of a device and are not intended to be limiting.Additionally, as those skilled in the art would realize, the describedembodiments may be modified in various different ways, all withoutdeparting from the spirit or scope of the present disclosure.

In the detailed description, for the purposes of explanation, numerousspecific details are set forth to provide a thorough understanding ofvarious embodiments. It is apparent, however, that various embodimentsmay be practiced without these specific details or with one or moreequivalent arrangements. In other instances, well-known structures anddevices are shown in block diagram form in order to avoid unnecessarilyobscuring various embodiments.

It will be understood that, although the terms “first,” “second,”“third,” etc., may be used herein to describe various elements,components, regions, layers and/or sections, these elements, components,regions, layers and/or sections should not be limited by these terms.These terms are used to distinguish one element, component, region,layer or section from another element, component, region, layer orsection. Thus, a first element, component, region, layer or sectiondescribed below could be termed a second element, component, region,layer or section, without departing from the spirit and scope of thepresent disclosure.

Spatially relative terms, such as “beneath,” “below,” “lower,” “under,”“above,” “upper,” and the like, may be used herein for ease ofexplanation to describe one element or feature's relationship to anotherelement(s) or feature(s) as illustrated in the figures. It will beunderstood that the spatially relative terms are intended to encompassdifferent orientations of the device in use or in operation, in additionto the orientation depicted in the figures. For example, if the devicein the figures is turned over, elements described as “below” or“beneath” or “under” other elements or features would then be oriented“above” the other elements or features. Thus, the example terms “below”and “under” can encompass both an orientation of above and below. Thedevice may be otherwise oriented (e.g., rotated 90 degrees or at otherorientations) and the spatially relative descriptors used herein shouldbe interpreted accordingly. Similarly, when a first part is described asbeing arranged “on” a second part, this indicates that the first part isarranged at an upper side or a lower side of the second part without thelimitation to the upper side thereof on the basis of the gravitydirection.

It will be understood that when an element, layer, region, or componentis referred to as being “on,” “connected to,” or “coupled to” anotherelement, layer, region, or component, it can be directly on, connectedto, or coupled to the other element, layer, region, or component, or oneor more intervening elements, layers, regions, or components may bepresent. However, “directly connected/directly coupled” refers to onecomponent directly connecting or coupling another component without anintermediate component. Meanwhile, other expressions describingrelationships between components such as “between,” “immediatelybetween” or “adjacent to” and “directly adjacent to” may be construedsimilarly. In addition, it will also be understood that when an elementor layer is referred to as being “between” two elements or layers, itcan be the only element or layer between the two elements or layers, orone or more intervening elements or layers may also be present.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of the presentdisclosure. As used herein, the singular forms “a” and “an” are intendedto include the plural forms as well, unless the context clearlyindicates otherwise. It will be further understood that the terms“comprises,” “comprising,” “have,” “having,” “includes,” and“including,” when used in this specification, specify the presence ofthe stated features, integers, steps, operations, elements, and/orcomponents, but do not preclude the presence or addition of one or moreother features, integers, steps, operations, elements, components,and/or groups thereof. As used herein, the term “and/or” includes anyand all combinations of one or more of the associated listed items.

As used herein, the term “substantially,” “about,” “approximately,” andsimilar terms are used as terms of approximation and not as terms ofdegree, and are intended to account for the inherent deviations inmeasured or calculated values that would be recognized by those ofordinary skill in the art. “About” or “approximately,” as used herein,is inclusive of the stated value and means within an acceptable range ofdeviation for the particular value as determined by one of ordinaryskill in the art, considering the measurement in question and the errorassociated with measurement of the particular quantity (i.e., thelimitations of, the measurement system). For example, “about” may meanwithin one or more standard deviations, or within ±30%, 20%, 10%, 5% ofthe stated value. Further, the use of “may” when describing embodimentsof the present disclosure refers to “one or more embodiments of thepresent disclosure.”

When a certain embodiment may be implemented differently, a specificprocess order may be performed differently from the described order. Forexample, two consecutively described processes may be performedsubstantially at the same time or performed in an order opposite to thedescribed order.

The electronic or electric devices and/or any other relevant devices orcomponents according to embodiments of the present disclosure describedherein may be implemented utilizing any suitable hardware, firmware(e.g. an application-specific integrated circuit), software, or acombination of software, firmware, and hardware. For example, thevarious components of these devices may be formed on one integratedcircuit (IC) chip or on separate IC chips. Further, the variouscomponents of these devices may be implemented on a flexible printedcircuit film, a tape carrier package (TCP), a printed circuit board(PCB), or formed on one substrate. Further, the various components ofthese devices may be a process or thread, running on one or moreprocessors, in one or more computing devices, executing computer programinstructions and interacting with other system components for performingthe various functionalities described herein. The computer programinstructions are stored in a memory which may be implemented in acomputing device using a standard memory device, such as, for example, arandom access memory (RAM). The computer program instructions may alsobe stored in other non-transitory computer readable media such as, forexample, a CD-ROM, flash drive, or the like. Also, a person of skill inthe art should recognize that the functionality of various computingdevices may be combined or integrated into a single computing device, orthe functionality of a particular computing device may be distributedacross one or more other computing devices without departing from thespirit and scope of the embodiments of the present disclosure.

Unless otherwise defined, all terms (including technical and scientificterms) used herein have the same meaning as commonly understood by oneof ordinary skill in the art to which the present inventive conceptbelongs. It will be further understood that terms, such as those definedin commonly used dictionaries, should be interpreted as having a meaningthat is consistent with their meaning in the context of the relevant artand/or the present specification, and should not be interpreted in anidealized or overly formal sense, unless expressly so defined herein.

FIG. 1 shows an example of performing a cell-balancing and depictingbalancing capacity and a changing trend of balancing current/poweraccording to a progress of cell-balancing.

In the present specification, the balancing channel means a dischargingpath corresponding to each cell, and the balancing channel may beconfigured to include at least one discharging resistor (or balancingresistor) and balancing switch. Further, the balancing capacity of eachcell represents a balancing standard of each cell (e.g., a capacity atwhich each cell should be discharged for cell-balancing).

Referring to FIG. 1, when the cell-balancing begins, a substantiallyidentical balancing current flows to the balancing channels (CH1, CH3,CH5, CH7, and CH9) regardless of balancing capacity. Accordingly, powerconsumption used per time by the cell-balancing in the balancingchannels (CH1, CH3, CH5, CH7, and CH9) is the same irrespective of thebalancing capacity. Therefore, discharging of the balancing channels(CH1, CH3, CH5, CH7, and CH9) is sequentially finished according to thebalancing capacity, and a sum of power consumption consumed by thedischarging in the balancing channels (CH1, CH3, CH5, CH7, and CH9) alsosequentially reduces.

Therefore, in designing a cell-balancing circuit, it may be useful todesign a discharging current in anticipation of power consumption underthe worst condition for performing a discharging for all of the cells tobe simultaneously balanced. Because of this consideration, there is alimit in increasing the balancing current for reducing thecell-balancing time.

A cell-balancing method according to embodiments of the presentdisclosure and a battery management system for performing the same willnow be described with reference to drawings.

FIG. 2 to FIG. 5 show examples of a battery pack for performing acell-balancing method according to embodiments of the presentdisclosure.

Referring to FIG. 2 to FIG. 5, battery packs 10 a, 10 b, 10 c, and 10 dmay include a battery module 100 and a battery management system (BMS).

The battery module 100 may include a plurality of cells connected inseries to each other.

The battery management system controls the battery packs 10 a, 10 b, 10c, and 10 d, and may include a battery integrated circuit (IC) 200 and abattery controller 300.

The battery IC 200 may detect a cell voltage, a charging and dischargingcurrent, a temperature of each cell configuring the battery module 100,and may control the cell-balancing on the battery module 100. Thebattery IC 200 may include an analog front end (AFE) IC and a cellvoltage monitoring (CVM) IC of the battery.

The battery IC 200 may include balancing switches (SWb) and a batterymonitoring circuit 210 for performing voltage detection, cell-balancingcontrol, and the like for the battery module 100.

The battery monitoring circuit 210 includes a voltage-detecting circuit,and through may detect a cell voltage of each cell configuring thebattery module 100. The voltage-detecting circuit is connected torespective ends of the corresponding cell through two input terminals(Cin) and two filter resistors (Rf), and it may detect the cell voltageof the corresponding cell.

When a cell voltage is detected, the battery monitoring circuit 210transmits the cell voltage to the battery controller 300. Upon receivinga cell-voltage-detecting result from the battery monitoring circuit 210,the battery controller 300 may control a cell-balancing and acharging/discharging of the battery module 100 based on thecell-voltage-detection result.

The battery packs 10 a, 10 b, 10 c, and 10 d may include acell-balancing circuit for controlling a balancing among the cellsconfiguring the battery module 100. In embodiments of the presentdisclosure, the cell-balancing of the battery module 100 is performed ina passive way, and the cell-balancing circuit may include resistors forforming a discharging path for cell-balancing of the cells, balancingswitches for opening and closing the discharging paths of the cells, anda battery monitoring circuit 210 for controlling the balancing switchesbased on cell-balancing control information provided by the batterycontroller 300.

For example with reference to FIG. 2, the cell-balancing circuitincludes, for each cell, two balancing resistors (Rb) respectivelyconnected between ends of a corresponding cell and the balancingterminals (Bin) and forming a discharging path, and a balancing switch(SWb) for allowing or blocking a cell-balancing current flow of thecorresponding cell according to control by the battery monitoringcircuit 210. The balancing switch (SWb) is connected between the twobalancing resistors (Rb) through the balancing terminals (Bin), and isconnected between the ends of the corresponding cell through the twobalancing resistors (Rb). Accordingly, when the balancing switch (SWb)is turned on, the balancing current flows through the balancingresistors (Rb) respectively connected to the ends of the correspondingcell to perform a discharging of the corresponding cell. On thecontrary, when the balancing switch (SWb) is turned off, the dischargingpath is blocked to thus block the balancing current flow of thecorresponding cell.

In the cell-balancing circuit shown with reference to FIG. 2, thebalancing terminals (Bin) respectively connected to the ends of thecells are formed separately from the input terminals (Cin) for voltagedetection, so a voltage detecting path of each cell is separated fromthe discharging path for a cell-balancing of each cell. The dischargingpath for two adjacent (or neighboring) cells may be partly shared bysharing the balancing terminal (Bin). Accordingly, the battery pack 10 amay perform a cell-balancing by dividing the cells configuring thebattery module 100 into an even-numbered group and an odd-numberedgroup, and by alternately turning on the balancing switches (SWb) of theeven-numbered group and the balancing switches (SWb) of the odd-numberedgroup.

For example with reference to FIG. 3, the cell-balancing circuitincludes, for each cell, a balancing resistor (Rb) connected between apositive electrode of a corresponding cell and the balancing terminal(Bin), a filter resistor (Rf) connected between a negative electrode ofthe corresponding cell and an input terminal (Cin), and a balancingswitch (SWb) for allowing or blocking the cell-balancing current flow ofthe corresponding cell according to control by the battery monitoringcircuit 210.

The balancing switch (SWb) is connected between two correspondingbalancing terminals (Bin). Further, when the balancing switch SWb isclosed, each balancing terminal (Bin) is connected to both ends of acorresponding cell (e.g., through the balancing resistor (Rb) connectedto the positive electrode of the corresponding cell and the filterresistor (Rf) connected to the negative electrode of the correspondingcell). Accordingly, when the balancing switch (SWb) is turned on, thebalancing current flows through the balancing resistor (Rb) and thefilter resistor (Rf) connected to both ends of the corresponding cell tothus progress a discharging of the corresponding cell.

In the cell-balancing circuit shown with reference to FIG. 3, a voltagedetecting path/voltage measuring path and a cell-balancing dischargingpath/cell balancing path of each cell share one filter resistor (Rf) andone input terminal (Cin). Also, the balancing terminal (Bin) is notshared between the cells, so cell-balancing may be independentlyperformed for each cell.

For example, with reference to FIG. 4, the cell-balancing circuitincludes, for each cell, a balancing resistor (Rb) connected between anelectrode of a corresponding cell, and the balancing terminal (Bin) anda balancing switch (SWb) for allowing or blocking the cell-balancingcurrent flow of the corresponding cell according to control by thebattery monitoring circuit 210. The balancing switch (SWb) is connectedbetween two balancing terminals (Bin). Further, one of the two balancingterminals (Bin) is connected to an electrode of the corresponding cellthrough the balancing resistor (Rb), and the other balancing terminal(Bin) is connected to the other electrode of the corresponding cell.Accordingly, when the balancing switch (SWb) is turned on, the balancingcurrent flows through the balancing resistor (Rb) connected to one ofthe respective ends of the corresponding cell to thus progress adischarging of the corresponding cell.

In the cell-balancing circuit shown with reference to FIG. 4, thebalancing terminals (Bin) connected to the ends of each cell existseparately from the input terminals (Cin) for voltage detection, andthereby a voltage detecting path and a cell-balancing discharging pathfor each cell are separated. In other embodiments, the balancingterminal (Bin) is partly shared by two adjacent cells.

For example with reference to FIG. 5, the cell-balancing circuitincludes, for each cell, a balancing resistor (Rb) connected between anelectrode of a corresponding cell, and both the balancing terminal (Bin)and a balancing switch (SWb) for allowing or blocking the cell-balancingcurrent flow of the corresponding cell according to control by thebattery monitoring circuit 210. The balancing switch (SWb) is connectedbetween two balancing terminals (Bin). Further, one of the two balancingterminals (Bin) is connected to one electrode of the corresponding cellthrough the balancing resistor (Rb), and the other balancing terminal(Bin) is connected to the other electrode of the corresponding cell.Accordingly, when the balancing switch (SWb) is turned on, the balancingcurrent flows through the balancing resistor (Rb) connected to anelectrode of the corresponding cell to thus progress a discharging ofthe corresponding cell.

In the cell-balancing circuit of FIG. 5, the balancing terminals (Bin)connected to both ends of each cell exist separately from the inputterminals (Cin) for voltage detection, and thereby a voltage detectingpath and a cell-balancing discharging path for each cell are separated.Further, the balancing terminals (Bin) for each cell are independentlyprovided.

Regarding FIG. 2 to FIG. 5, the balancing switch (SWb) may be configuredwith field effect transistors (FET).

FIG. 2 to FIG. 5 depict the case in which balancing switches (SWb) areincluded in a battery IC 200. However, an embodiment of the presentdisclosure is not limited thereto, and the balancing switches (SWb) maybe located outside the battery IC 200.

A cell-balancing method according to embodiments of the presentdisclosure will now be described with reference to accompanyingdrawings. Embodiments of the present disclosure described below may beperformed by the battery packs (e.g., battery controller 300 and batteryIC 200) described with reference to FIG. 2 to FIG. 5.

A cell-balancing method according to a first embodiment of the presentdisclosure will now be described with reference to FIG. 6 to FIG. 8.

FIG. 6 shows a cell-balancing method according to a first embodiment ofthe present disclosure. FIG. 7 and FIG. 8 show examples of balancingcapacity and a changing trend of average balancing current/power when acell-balancing control method according to a first embodiment of thepresent disclosure is used. FIG. 9 shows an example of a related artcell-balancing control timing diagram, and FIG. 10 shows an example of acell-balancing control timing diagram when a cell-balancing methodaccording to a first embodiment of the present disclosure is applied.

Referring to FIG. 6, according to a first embodiment of the presentdisclosure, the battery packs 10 a, 10 b, and 10 c periodically detect acell voltage of each cell configuring the battery module 100 through thebattery IC 200 (S100).

In S100, the battery IC 200 includes a voltage-detecting circuit, and itmay detect the cell voltage of each cell through the same.

The cell voltage detected by the battery IC 200 is transmitted to thebattery controller 300, and based on this, the battery controller 300determines whether a cell-balancing on the battery module 100 iswarranted (S101).

When the cell-balancing is determined to be warranted, the batterycontroller 300 calculates balancing capacity of each cell subject tobalancing (referred to as a balancing target cell, hereinafter) based onthe cell voltage of each cell (S102).

In S102, the battery controller 300 may calculate an average cellvoltage on the cells configuring the battery module 100, and maycalculate balancing capacity of each cell from a respective differencebetween the calculated average cell voltage and the cell voltage of eachcell.

The battery controller 300, when the balancing capacity for each thebalancing target cell is calculated, sets a duty cycle of thecorresponding balancing switch (SWb) based on the calculated balancingcapacity (S103). In the present specification, the duty cycle of thebalancing switch (SWb) may mean the ratio of a turn-on time of thebalancing switch to the sum of the turn-on time and a turn-off time ofthe (SWb), and may mean the ratio of duration in which the balancingswitch (SWb) is turned on within one balancing cycle.

The duty cycle calculated for each balancing switch (SWb) is included incell-balancing control information, and is then transmitted to thebattery IC 200. The battery IC 200 controls the turn-on/off of thebalancing switch (SWb) (S104) based on the duty cycle for each balancingswitch (SWb). In this instance, when the balancing switch (SWb) ispulse-driven, the average balancing current/power of the correspondingdischarging path is proportional to the duty cycle of the switch (SWb).

In S103, the battery controller 300 may set the duty cycle of thebalancing switch (SWb) corresponding to each balancing target cell basedon the ratio(s) of balancing capacities of the balancing target cells.

FIG. 7 and FIG. 8 show balancing capacity when a duty cycle of abalancing switch is controlled according to balancing capacity, and achanging trend of average balancing current/power.

For example with reference to FIG. 7, the duty cycle of the balancingswitch (SWb) configuring the balancing channels CH1, CH3, CH5, CH7, andCH9 is set corresponding to the balancing capacity ratio of thecorresponding balancing target cell. That is, the battery controller 300sets respective ratios of balancing capacities of the balancing targetcells and the respective ratios of duty cycles of correspondingbalancing switches (SWb) to be substantially identical. When set asdescribed, the balancing channels CH1, CH3, CH5, CH7, and CH9concurrently starting a cell-balancing may have a substantiallyidentical balancing finishing time. Further, the sum of powerconsumption used by the cell-balancing in all of the balancing channels(balancing target cells) is maintained until the cell-balancingfinishes, and increased or maximum power consumption caused by thecell-balancing also is reduced by the average power consumption.

Hereinafter, by exemplifying the case in which the ratio of balancingcapacity of three balancing target cells A, B, and C is A:B:C=1:0.5:0.2,and the balancing current in each balancing channel is IA, an effect ofreducing maximum power consumption in the case of setting the duty cycleof the balancing switch based on balancing capacity will be described indetail.

When the duty cycle of the balancing target cells A, B, and C is set tobe D_(CA):D_(CB):D_(CC)=1:0.5:0.2 like the ratio of balancing capacityaccording to the method shown with reference to FIG. 7, the averagebalancing current of the balancing target cells A, B, and C compared tothe maximum balancing current becomes A=IA, B=0.51A, and C=0.2IA.Further, the average power consumed by the balancing resistor (R) ofeach balancing channel becomes P_(A)=(IA)²×R, P_(B)=(0.5IA)²×R, andP_(C)=(0.2IA)²×R. Therefore, the sum of power consumption used by thecell-balancing in the three balancing target cells A, B, and C becomesP_(total)=P_(A)+P_(B)+P_(C)=(IA)²×R+(0.5IA)²×R+(0.2IA)²×R=(1+0.25+0.04)×(IA)²×R=1.29×(IA)²×R.

When the cell-balancing method described with reference to FIG. 1 isapplied to the same case, the same balancing current (IA) flows to thebalancing target cells A, B, and C such that power consumption used bythe balancing resistor (R) becomes P_(A)=P_(B)=P_(C)=(IA)²×R. In thisinstance, the balancing target cells A, B, and C have differentbalancing capacities such that the cell-balancing finishing time of thebalancing target cells A, B, and C, and the sum of power consumptioncaused by the cell-balancing of the balancing target cells A, B, and Cgradually reduces each time the cell-balancing on one of the balancingtarget cells finishes.

For example, the sum of power consumption caused by the cell-balancingwhen the balancing starts is P_(total)=3×(IA)²×R, the sum of powerconsumption caused by the cell-balancing after the balancing on the cellC finishes is P_(total)=2×(IA)²×R, the sum of power consumption causedby the cell-balancing after the cell-balancing on the cell B finishes isP_(total)=(IA)²×R, and when the cell-balancing on the cell A finishes,the cell-balancing on the balancing target cells ends.

In comparison of the above-noted two cases, as shown in FIG. 7, powerconsumption in the case of controlling the duty cycle of the balancingswitch according to the ratio of balancing capacity is constant to beP_(total)=1.29×(IA)²×R, and power consumption in the case of performinga cell-balancing without controlling the duty cycle as shown in FIG. 1is P_(total)=3×(IA)²×R to the maximum when the cell-balancing starts,and it gradually reduces as the cell-balancing progresses. In comparisonof the maximum power consumption of the above-noted two cases, when theduty cycle of the balancing switch is controlled according to the ratioof balancing capacity, the maximum power consumption reduces to about43% in the case of performing a cell-balancing without controlling theduty cycle.

Therefore, in a first embodiment of the present disclosure, as shown inFIG. 8, the discharging current for a cell-balancing may be increased sothat power consumption caused by a cell-balancing may increase to anallowable power considering radiation performance of the substrate onwhich a cell-balancing circuit is mounted such that the balancing timemay be reduced.

Assuming that allowable power in consideration of radiation performanceof the substrate is 3×(IA)²×R, when the present balancing current is IAand the allowable balancing current is IB, it becomes that1.29×(IB)²×R=3×(IA)²×R and

${\frac{IB}{IA} = {\sqrt{\frac{3}{1.29}} \cong 1.44}},$

so IA may be allowed to increase up to IB=1.44×IA.

The battery pack 10 a shown in FIG. 2 has a configuration such that itshares a balancing terminal (Bin) among adjacent (or neighboring) cells,and the balancing switches (SWb) might not be simultaneously turned onfor the adjacent cells sharing the balancing terminal (Bin).

Regarding the above-configured conventional battery pack 10 a, as shownin FIG. 9, the cell-balancing is performed by distinguishing the cellsconfiguring the battery module 100 into an even-numbered group and anodd-numbered group, and by alternately turning on the balancing switches(SWb) of the even-numbered group and the balancing switches (SWb) of theodd-numbered group. In this instance, a section in which the balancingswitches (SWb) of the odd-numbered cell group and the balancing switches(SWb) of the even-numbered cell group are turned on/off is fixed.Accordingly, in a section in which the balancing switches (SWb) of oneof the groups are turned on, the balancing switches (SWb) of the othergroup may be maintained to be turned off.

As described, when the cell-balancing method according to a firstembodiment of the present disclosure is applied to the battery pack(e.g., the battery pack 10 a shown in FIG. 2) for performing acell-balancing by alternately performing a balancing to adjacent cells,and when the greatest balancing capacity (Q_(b)) calculated for therespective balancing target cells is denoted as Q_(b) _(_) _(max), theduty cycle (D_(Ci)) of the balancing switch (SWb) corresponding to eachthe balancing target cell may be expressed as in Equation 1.

D _(Ci) =Q _(b) /Q _(b) _(_) _(max)×50%   Equation 1

When the balancing current flowing through the corresponding dischargingpath for the duration corresponding to the duty cycle (D_(Ci)) is givenas I_(b), the average balancing current (I_(b) _(_) _(ave)) flowingthrough the discharging path of the balancing target cell in onebalancing cycle (T) may be given as like in Equation 2.

I _(b) _(_) _(ave) =I _(b) ×D _(Ci)   Equation 2

Further, the balancing current amount (I_(total)) actually discharged inthe total balancing time (T_(b)) is expressed in Equation 3.

I _(total) =I _(b) _(_) _(ave) ×T _(b)   Equation 3

Referring to Equations 1 to 3, the total balancing time (T_(b)) may becalculated by using Equation 4.

T _(b) =I _(total) /I _(b) _(_) _(ave) =I _(total)/(I _(b) ×D _(Ci))=I_(total)/(I _(b)×(Q _(b) /Q _(b) _(_) _(max)×50%))   Equation 4

Also, the discharging amount performed within the balancing time (T_(b))is designed for the purpose of balancing capacity (Q_(b)), so Equation 4may be changed into Equation 5.

T _(b) =Q _(b) _(_) _(max)/(I _(b)×50%)   Equation 5

Referring to Equation 5, the balancing time (T_(b)) may be determined bythe values of Q_(b) _(_) _(max) and I_(b) regarding all of the balancingtarget cells (e.g., balancing channels).

FIG. 10 illustrates a timing diagram when a cell-balancing is performedaccording to a method described with reference to Equations 1 to 5.

Referring to FIG. 10, the total balancing time (T_(b)) on the balancingtarget cells is determined by the duty cycle (D_(Ci)) of a balancingchannel CH1 with the maximum balancing capacity. However, thecell-balancing is alternately performed by the odd-numbered dischargingchannel and the even-numbered discharging channel, so the cell-balancingefficiency may be limited.

To solve the above-noted problem, in the cell-balancing method accordingto a second embodiment of the present disclosure, while the duty cycleof the balancing switches (SWb) is based on-the balancing capacity ratioamong the balancing target cells, the duty cycle of the balancingswitches (SWb) is scaled so that sums of duty cycles of the two adjacentcells may be less than or equal to a maximum of 100%. Therefore, onebalancing on one of two adjacent cells is turned on while the balancingof the other is turned off to prevent two adjacent cells fromsimultaneously being turned on. Accordingly, it becomes possible to setthe duty cycle of one cell to be greater than 50% through a dutyscaling, thereby increasing the cell-balancing efficiency.

A cell-balancing method according to a second embodiment of the presentdisclosure will now be described in detail with reference to FIG. 11 toFIG. 14.

FIG. 11 shows a cell-balancing method according to a second embodimentof the present disclosure.

Referring to FIG. 11, according to a second embodiment of the presentdisclosure, the battery packs 10 a, 10 b, and 10 c periodically detectcell voltages of the respective cells for configuring the battery module100 through the battery IC 200 (S200).

The cell voltage detected by the battery IC 200 is transmitted to thebattery controller 300, and the battery controller 300 determineswhether a cell-balancing on the battery module 100 is warranted (S201).

The battery controller 300, when it is determined that a cell-balancingis warranted, calculates the balancing capacity of the respectivebalancing target cells’ subject to a balancing based on the cellvoltages of the cells (S202).

The battery controller 300, when balancing capacity on the respectivebalancing target cells is calculated, sets the duty cycle of thecorresponding balancing switch (SWb) based on the calculated balancingcapacity (S203).

In S203, the battery controller 300 may set the ratio of balancingcapacity of the balancing target cells and the ratio of the duty cycleof the balancing switch (SWb) corresponding to the balancing targetcells to be substantially identical.

When the duty cycle of the balancing switches (SWb) is set based on thebalancing capacity ratio among the balancing target cells, the batterycontroller 300 scales the duty cycle of the balancing switches (SWb) sothat the sum of the duty cycles of two adjacent cells may be less thanor equal to a maximum of 100% (S204).

The duty cycle scales corresponding to S204 may be included incell-balancing control information and may be transmitted to the batteryIC 200, and the battery IC 200 controls turn-on/off of the balancingswitches (SWb) according to the duty cycle (S205).

A method for scaling duty cycles of balancing switches (SWb) in S204will now be described in detail.

FIG. 12 and FIG. 13 show a basic concept of a duty scaling in acell-balancing method according to a second embodiment of the presentdisclosure.

Referring to FIG. 12 and FIG. 13, according to a second embodiment ofthe present disclosure, a plurality of cells configuring the batterymodule 100 are divided into an odd-numbered cell group and aneven-numbered cell group. In FIG. 12 and FIG. 13, the discharging pathof the balancing target cell included in the odd-numbered cell group isdenoted to be an odd-numbered balancing channel, and the dischargingpath of the balancing target cell included in the even-numbered cellgroup is denoted to be an even-numbered balancing channel.

Referring to FIG. 12, when the duty cycle of the balancing switch (SWb)for the odd-numbered balancing channel is defined to be x(%), thebalancing switch (SWb) maintains the turn-on state for the durationcorresponding to the duty cycle (x(%)) regarding the odd-numberedbalancing channel, and the balancing switch (SWb) maintains the turn-offstate for the period of 100-x(%) until the corresponding balancing cycleends.

When the duty cycle of the balancing switch (SWb) for the even-numberedbalancing channel is defined to be y(%), the balancing switch (SWb) ismaintained at the turn-off state for the period of 100-y(%) of thebalancing cycle regarding the even-numbered balancing channel, and thebalancing switch (SWb) is maintained at the turn-on state for theduration corresponding to the duty cycle (y(%)).

Referring to FIG. 13, the balancing switch (SWb) is maintained at theturn-on state for the duration corresponding to the duty cycle (y(%))regarding the even-numbered balancing channel, and the balancing switch(SWb) maintains the turn-off state for the period of 100-y(%) until thecorresponding balancing cycle ends.

The balancing switch (SWb) is maintained at the turn-off state for theperiod of 100-x(%) of the balancing cycle regarding the odd-numberedbalancing channel, and the balancing switch (SWb) is maintained at theturn-on state for the duration corresponding to the duty cycle (x(%)).

As shown in FIG. 12 and FIG. 13, when the cell-balancing of balancingchannels is controlled, the sum (x+y) of the duty cycles of two adjacentcells may satisfy the condition of x+y≤100% so that the balancingswitches (SWb) of the two adjacent cells may not be simultaneouslyturned on. Therefore, the cell-balancing method according to a secondembodiment of the present disclosure scales the duty cycle of thebalancing switches (SWb) in the range satisfying the limit condition.

When the maximum value from among balancing capacity (Q_(b)) ofrespective balancing target cells is defined to be Q_(b) _(_) _(max),the duty cycle (D_(Ci)) of the balancing switch (SWb) set correspondingto the balancing capacity (Q_(b)) may be expressed as in Equation 6.

D _(Ci)=(Q _(b))/(Q _(b) _(_) _(max))×k   Equation 6

In Equation 6, k may be set with a random value, and it may be set to be50% for the purpose of comparison with a related art example.

The summation value (D_(CiCj)) of the duty cycles for each of cellcombinations composed of two adjacent cells (i, j) based on Equation 6may be expressed in Equation 7.

D _(CiCj) =D _(Ci) +D _(Cj)   Equation 7

When the maximum value from among values D_(CiCj) calculated throughEquation 7 is defined to be D_(CiCj) _(_) _(max), and when a scalefactor (w) is calculated so that the value may be 100%, (w) may beexpressed as in Equation 8.

w=(100%/D _(CiCj) _(_) _(max))   Equation 8

When the scale factor (w) is calculated through Equation 8, the batterycontroller 300 multiplies the scale factor (w) and the duty cycle(D_(Ci)) of the balancing switches (SWb) calculated through Equation 6to scale the duty cycle (D_(Ci)) of the balancing switches (SWb).

D_(Ci) _(_) _(scale)=(Q _(b))/(Q _(b) _(_) _(max))×50%×w   Equation 9

Equation 9 may be expressed as Equation 10.

D _(Ci) _(_) _(scale)=(Q _(b))/(Q _(b) _(_) _(max))×50%/D _(CiCj) _(_)_(max)   10

Referring to Equation 10, the duty cycle (D_(Ci)) of respectivebalancing target cells depends on the maximum summation value (D_(CiCj)_(_) _(max)) of the duty cycles (D_(Ci), D_(Cj)) between two adjacentcells.

When the maximum summation value (D_(CiCj) _(_) _(max)) of the dutycycles (D_(Ci), D_(Cj)) of two adjacent cells is 100%, and when twocells of which the duty cycles (D_(Ci), D_(Cj)) are each the maximumvalue (50%) are adjacent to each other, the duty cycle (D_(Ci) _(_)_(scale)) scaled by Equation 10 becomes substantially identical with theduty cycle D_(C) calculated through Equation 1 in a first embodiment ofthe present disclosure.

However, when one of the two adjacent cells has the duty cycle (D_(Ci),D_(Cj)) that is not the maximum value (50%), D_(Ci) _(_) _(scale) scaledthrough Equation 10 may increase to be greater than D_(Ci) calculatedthrough Equation 1 in a first embodiment of the present disclosure.

FIG. 14 shows a relationship between total balancing capacity of allbalancing channels and a balancing time when a cell-balancing methodaccording to a second embodiment of the present disclosure is applied,exemplifying a case in which the battery module 100 includes twelve 37Ah cells connected in series to each other and in which the balancingcurrent (I_(b)) is 100 mA.

Referring to FIG. 14, when the cells with the most balancing capacityare adjacent to each other (Case 1), a discharging time becomes the caseof performing a cell-balancing according to the existing methoddescribed with reference to FIG. 1 irrespective of balancing capacitiesof the remaining balancing target cells. However, regarding other cases(Case 2 and Case 3), the balancing time may be reduced corresponding tothe maximum value from among the summation of balancing capacity amongadjacent cells.

FIG. 15 shows an example of a case in which a duty scaling is applied toa timing diagram of FIG. 10.

Referring to FIG. 15, the maximum summation value (D_(CiCj) _(_) _(max))of the duty cycles (D_(Ci), D_(Cj)) between two adjacent cells in FIG.10 is given as D_(CiCj) _(_) _(max)=(33+50)%=83%, which is the summationof the duty cycles of balancing channels CH1 and CH2. When this issubstituted into Equation 8, the scale factor (w) is determined asw=(100%/83%)=1.2.

As shown in FIG. 15, when the calculated scale factor (w=1.2) is appliedto the duty cycles of the respective balancing channels shown in FIG.10, the duty cycles of the balancing channels CH1, CH2, CH6, CH7, andCH9 increase to 60%, 40%, 30%, 12%, and 6% from 50%, 33%, 25%, 10%, and5%, respectively. As described, when the cell-balancing is performedbased on the scaled duty cycles, the average balancing current increasesby 20% to thus reduce the balancing time by about 20% in comparison tothe case of performing a cell-balancing based on the timing diagramshown in FIG. 10.

When the average balancing current is increased by increasing thebalancing current or increasing the discharging efficiency according tofirst and second embodiment of the present disclosure, generation ofheat by the balancing resistor may be an issue.

To solve the issue of heat generation, a cell-balancing method accordingto a third embodiment of the present disclosure described below mayacquire the heat radiation performance of the substrate on which acell-balancing circuit is located by managing power consumption of allof the balancing resistors in addition to individual power consumptionof each balancing resistor.

Power generated by the balancing current generates heat by the balancingresistor, and the heat generated by the balancing resistor is mostlyradiated through a wiring pattern of the substrate according to athermal conduction method. Therefore, the configuration of the substrateprovided around the balancing resistor or the wiring pattern mayinfluence the heat radiation performance. The balancing resistors areclose to each other on the actual substrate. Hence, the heat radiationperformance of the substrate may be obtained by managing the powerconsumption of the balancing resistors in addition to individual powerconsumption of each balancing resistor.

A cell-balancing method according to a third embodiment of the presentdisclosure will now be described with reference to FIG. 16 and FIG. 17.

FIG. 16 shows a cell-balancing method according to a third embodiment ofthe present disclosure.

Referring to FIG. 16, the battery packs 10 a, 10 b, and 10 cperiodically detect the cell voltages of the respective cellsconfiguring the battery module 100 through the battery IC 200 accordingto a third embodiment of the present disclosure (S300).

The cell voltages detected by the battery IC 200 are transmitted to thebattery controller 300, and the battery controller 300 determineswhether a cell-balancing on the battery module 100 is warranted (S301).

The battery controller 300, when a cell-balancing is determined to bewarranted, calculates balancing capacity of the respective balancingtarget cell subject based on the cell voltages of the cells (S302).

When the balancing capacity for the respective balancing target cells iscalculated, the battery controller 300 sets the duty cycles of thebalancing switches (SWb) based on the calculated balancing capacity(S303).

In S303, the battery controller 300 may set the ratio of balancingcapacities of the balancing target cells and the ratio of the dutycycles of the balancing switches (SWb) of the balancing target cells tobe substantially identical.

In S303, regarding the battery pack (e.g., the battery pack 10 a shownin FIG. 2) to which a cell-balancing is performed according to a methodfor alternately performing balancing on adjacent cells, when the dutycycles of the balancing switches

(SWb) are set based on the balancing capacities among balancing targetcells, the battery controller 300 may scale the duty cycles of thebalancing switches (SWb) so that the summation of duty cycles betweentwo adjacent cells may be less than or equal to a maximum of 100% asexpressed in Equation 9.

When the duty cycles of the respective balancing switches (SWb) are setaccording to the balancing capacity through S303, the average balancingcurrents of the respective balancing channels are maintained from thebalancing start time to the ending time, and the heat generated as aresult may be substantially constant. Therefore, the battery controller300 may scale the duty cycles of the balancing switches (SWb) based on apower consumption upper limit allowable to the balancing channels as awhole (S304). Here, the power consumption upper limit is provided as aregister setting value inside the battery IC 200, may be modified bysoftware, and may be improved or optimized by checking the generation ofheat on the actual substrate in a product developing stage.

The duty cycles scaled through S304 are included in cell-balancingcontrol information and are then transmitted to the battery IC 200, andthe battery IC 200 controls the turn-on/off of the balancing switches(SWb) (S305).

In S304, the battery controller 300 sums the balancing capacities of thebalancing target cells to calculate a total power consumption generatedby balancing, and compares the total power consumption and a powerconsumption upper limit. When the total power consumption generated by abalancing exceeds the power consumption upper limit, the batterycontroller 300 scales the duty cycles of the balancing switches (SWb) toreduce the power consumption used by a balancing.

A method for scaling duty cycles of balancing switches (SWb) based on apower consumption upper limit in S304 will now be described.

While the duty cycle (D_(Ci) _(_) _(scale)) of the balancing switch(SWb) is set by use of Equation 9, the average balancing current (I_(b)_(_) _(ave) _(_) _(Ci)) of the respective balancing channels may becalculated as in Equation 11.

I _(b) _(_) _(ave) _(_) _(Ci) =I _(b) ×D _(Ci) _(_) _(scale)   Equation11

When the average balancing current (I_(b) _(_) _(ave) _(_) _(Ci)) iscalculated for the respective balancing channels through Equation 11,the battery controller uses the same to calculate the current scalefactor (w_(c)) as expressed in Equation 12.

w _(c) =I _(Limit)/(ΣI _(b) _(_) _(ave) _(_) _(Ci))   Equation 12

In Equation 12, I_(Limit) is a current upper limit allowable on thesubstrate on which the balancing resistors are mounted, and ΣI_(b) _(_)_(ave) _(_) _(Ci) is the sum of average balancing currents in all of thebalancing target channels.

When the current scale factor (w_(c)) is calculated through Equation 12,the battery controller 300 applies the same to the duty cycle (D_(Ci)_(_) _(scale)) scaled through Equation 10 as expressed in Equation 13.

D _(Ci) _(_) _(limit) =D _(Ci) _(_) _(scale)×(w _(c))=(Q _(b))/(Q ₁₃_(b) _(_) _(max))×50%×w×w _(c)   Equation 13

Referring to Equation 13, the heat radiation performance of thesubstrate may be obtained by applying the current scale factor (w_(c))to the duty cycle (D_(Ci) _(_) _(scale)) of the balancing target cellsin a third embodiment of the present disclosure.

FIG. 17 shows a relationship between total balancing capacity of allbalancing channels and a balancing time when a cell-balancing methodaccording to a third embodiment of the present disclosure is applied,exemplifying the case in which the battery module 100 includes twelve 37Ah cells connected in series to each other and the balancing current(I_(b)) is 200 mA.

Referring to FIG. 17, the balancing time is determined corresponding tothe maximum value from among the balancing capacities among adjacentcells. In a third embodiment of the present disclosure, when the totalbalancing capacity of the balancing target cells exceeds a limit (e.g.,a predetermined power consumption upper limit), the duty cycles of thebalancing switches (SWb) reduce by the current scale factor, and thebalancing time accordingly increases.

However, when the duty cycle is reduced by using a current scale factor,the balancing time is reduced in comparison with the case in which thebalancing current is reduced (e.g., I_(b)=100 mA) to the levelcorresponding to the power limit, so efficient discharging may progresswithin a range of allowable power.

Further, in the described third embodiment of the present disclosure,the power consumption upper limit of the balancing resistors is set inconsideration of the heat radiation performance of the substrate, andthe duty cycles of the balancing switches (SWb) are controlled so thatthe total/entire power consumption used by a cell-balancing may notexceed the upper limit.

However, the power consumption individually used by the respectivebalancing resistors differs in accordance with the respective duty cycle(or the duration) of the balancing switch (SWb). Accordingly, deviationor variation exists with respect to a respective amount of heatgenerated by the balancing resistors. When the power consumption used byan entirety of the balancing resistors is the same, the amount of heatgenerated by the substrate may differ because of the difference of theduty cycles (or the duration) of the respective balancing switches(SWb).

Hence, in a fourth embodiment of the present disclosure described below,when the duty cycle (or the on duration) of the balancing switch (SWb)is set, the cell-balancing efficiency may be increased by limiting powerin consideration of a power consumption deviation among balancingresistors.

A cell-balancing method according to a fourth embodiment of the presentdisclosure will now be described with reference to FIG. 18 and FIG. 19.

FIG. 18 shows a cell-balancing method according to a fourth embodimentof the present disclosure.

Referring to FIG. 18, according to a fourth embodiment of the presentdisclosure, the battery packs 10 a, 10 b, and 10 c periodically detectthe cell voltages of the cells configuring the battery module 100through the battery IC 200 (S400).

The cell voltages detected by the battery IC 200 are transmitted to thebattery controller 300, and the battery controller 300 determineswhether a cell-balancing on the battery module 100 is warranted (S401).

The battery controller 300, when a cell-balancing is determined to bewarranted, calculates a balancing capacity for each of the respectivebalancing target cells that are subject to a balancing based on the cellvoltages of the cells (S402).

When the balancing capacity on the balancing target cells is calculated,the battery controller 300 sets the duty cycle of the correspondingbalancing switch (SWb) based on the calculated balancing capacity(S403).

In S403, the battery controller 300 may set the ratio(s) betweenbalancing capacities of the balancing target cells and theratio()between the duty cycles of the corresponding balancing switchesof the balancing target cells (SWb) to be substantially identical.

In S403, regarding the battery pack (e.g., the battery pack 10 a shownin FIG. 2) to which a cell-balancing is performed according to a methodfor alternately performing a balancing on adjacent cells, the batterycontroller 300 may scale the duty cycles of the balancing switches (SWb)so that the summation of duty cycles between two adjacent cells may beless than or equal to a maximum of 100% as expressed in Equation 9.

When the duty cycles of the balancing switches (SWb) are set accordingto the corresponding balancing capacity through S403, the batterycontroller 300 may scale the duty cycles of the balancing switches (SWb)based on the power consumption upper limit allowable to all of thebalancing channels and the current upper limit allowable for theindividual balancing channel (S404).

Here, the power consumption upper limit allowable for all of thebalancing channels and the current upper limit allowable for onebalancing channel are provided as register setting values inside thebattery IC 200. However, they may be modifiable (e.g., by usingsoftware), and they may be improved or optimized by checking or testingheat generation on the actual substrate in the product developing stage.

The duty cycles scaled through S404 are included in cell-balancingcontrol information and are transmitted to the battery IC 200, and thebattery IC 200 controls on time/off time (e.g., turn-on/off operations)of the balancing switches (SWb) (S405).

A method for scaling duty cycles of balancing switches (SWb) in S404will now be described in detail.

When the duty cycle (or duration) of the balancing switch (SWb) is 100%,power consumption corresponding to a balancing resistor is the greatest(e.g., at a maximum), and the amount of heat generated is also thegreatest/at a maximum. As the number of balancing channels discharged bya cell-balancing increases, the heat radiation performance of thesubstrate is deteriorated.

In consideration of this point, in a fourth embodiment of the presentdisclosure, Equation 12 for calculating a current scale factor (w_(c))will be substituted into Equation 14.

w _(c)=(I _(Limit) _(_) _(total)/(ΣI _(b) _(_) _(ave) _(_) _(Ci)))×(I_(Limit) _(_) _(Ci) /I _(b) _(_) _(ave) _(_) _(Ci))   Equation 14

In Equation 14, I_(Limit) _(_) _(total) is a current upper limit that issuitable for the balancing channels as a group, and I_(Limit) _(_) _(Ci)is a current upper limit for a single balancing channel. Also, I_(b)_(_) _(ave) _(_) _(Ci) is an average balancing current of balancingchannels, and ΣI_(b) _(_) _(ave) _(_) _(Ci) is an average balancingcurrent of the balancing channels as a whole.

When the current scale factor (w_(c)) corresponding to the balancingswitches (SWb) is calculated through Equation 14, the battery controller300 substitutes the same into Equation 13 to finally acquire the dutycycles (D_(Ci) _(_) _(limit)) of the balancing switches (SWb).Accordingly, the power consumption at the time of performing a balancingmay be limited by considering local generation of heat in thecell-balancing circuit in addition to the overall heat radiationperformance of the substrate on which the cell-balancing circuit ismounted.

FIG. 19 shows a relationship between an average balancing current inrespective balancing channels and power consumption of all of thebalancing resistors (e.g., balancing resistance total power) when acell-balancing method according to a fourth embodiment of the presentdisclosure is applied. In the present example, the battery module 100includes twelve 37 Ah cells connected in series to each other and thebalancing current (I_(b)) is 100 mA.

Referring to FIG. 19, when the balancing resistance total power isgreater than the upper limit (1.45 W) of power consumption allowable forthe balancing channels as a group, the duty cycle set for all of thebalancing channels is controlled to reduce the average consumptioncurrent of the balancing channels.

Further, in an example of the fourth embodiment of the presentdisclosure, the current upper limit (70 mA) is set for the individualbalancing channel, and the duty cycle of the balancing switch (SWb) soas to reduce the average consumption current regarding the balancingchannel that exceeds the current upper limit.

The cell-balancing performing timing may be divided into a key-on stateof the battery pack, and a key-off state. In the present specification,the key-on state corresponds to a state in which the battery pack iscurrently discharged by an operation of a set or device (e.g., avehicle) on which the battery pack is mounted, or in which the batterypack is currently charged by a charging device.

At the key-on time of the battery pack, a cell-balancing may beperformed in an environment in which the battery management system (BMS)periodically performs functions such as diagnosis. Therefore, when thetime used for a cell-balancing is relatively long, it may be useful totemporarily pause the cell-balancing because of diagnosis, which maymake it more difficult to set the duty cycle.

To solve this problem, in a fourth embodiment of the present disclosure,when a cell-balancing is performed, the cell-balancing process isdivided into a plurality of steps to be discretely performed. In a fifthembodiment of the present disclosure, the balancing performing time isobtained using a counter, and when the balancing performing time becomesequivalent to the duty-setting value (e.g., a duration value), thebalancing stops.

Through this, the “On” duty controls becomes allowable within a period(e.g., a predetermined period). The cell-balancing is performed up tothe balance capacity that is the final target by continuing theabove-noted operation.

A cell-balancing method according to a fifth embodiment of the presentdisclosure will now be described with reference to FIG. 20 to FIG. 24.

FIG. 20 shows a cell-balancing method according to a fifth embodiment ofthe present disclosure, and depicts an example of performing acell-balancing in a key-on state.

Referring to FIG. 20, according to a fifth embodiment of the presentdisclosure, the battery packs 10 a, 10 b, and 10 c periodically detectthe cell voltages of respective cells configuring the battery module 100through the battery IC 200 (S500).

The cell voltages detected by the battery IC 200 are transmitted to thebattery controller 300, and the battery controller 300 determineswhether a cell-balancing on the battery module 100 is warranted (S501).

The battery controller 300, when a cell-balancing is determined to bewarranted, calculates one or more balancing capacities of the balancingtarget cells subject to a balancing based on the cell voltages ofrespective cells (S502).

The battery controller 300, when the balancing capacity on the balancingtarget cells is calculated, sets the duty cycle of the correspondingbalancing switch (SWb) based on the calculated balancing capacity(S503).

In S503, the battery controller 300 may set the ratio between balancingcapacities of balancing target cells and the ratio between the dutycycles of the corresponding balancing switches (SWb) of the balancingtarget cells to be substantially identical.

In S503, when the duty cycles of the balancing switches (SWb) are setbased on the ratio between balancing capacities of balancing targetcells, the battery controller 300 may scale the duty cycles of thebalancing switches (SWb) so that the sum of duty cycles between twoadjacent cells may be less than or equal to a maximum of 100% as inS204.

In S503, when the duty cycles of the balancing switches (SWb) are setbased on the ratio between balancing capacities of balancing targetcells, the battery controller 300 may scale the duty cycles of thebalancing switches (SWb) based on the power consumption upper limitallowable for the balancing channels as in S304.

In S503, when the duty cycles of the balancing switches (SWb) are setaccording to the balancing capacity, the battery controller 300 mayscale the duty cycles of respective balancing switches (SWb) based onthe power consumption upper limit allowable for the balancing channelsas a whole, and the current upper limit allowable for the individualbalancing channel as in S404.

The duty cycles calculated for the respective balancing switches (SWb)through S503 are included in cell-balancing control information, and aretransmitted to the battery IC 200. The battery IC 200 controls therespective balancing switches (SWb) to turn them on and off. In thisinstance, the battery controller 300 repeats the cell-balancing taskaccording to the duty cycle to thus control the turn-on/off of thebalancing switches (SWb) (S504).

In S504, the cell-balancing task is a task performed for a shorterperiod than the balancing cycle, and it turns on the balancing switch(SWb) for a period (e.g., a predetermined period) while the task isexecuted. The battery controller 300 may repeat the cell-balancing taskso that the total time in which a balancing discharging is performed bya repetition execution of the cell-balancing task within the balancingcycle may be substantially identical with the duration of thecorresponding balancing switch (SWb).

FIG. 21 shows a cell-balancing control circuit for performing acell-balancing method according to a fourth embodiment of the presentdisclosure shown in FIG. 20. FIG. 22 shows a chart of a cell-balancingcontrol timing diagram of a cell-balancing control circuit shown in FIG.21, and FIG. 23 shows a balancing control timing diagram using acell-balancing control circuit shown in FIG. 21. The cell-balancingcontrol circuit shown in FIG. 21 may be included in the batterymonitoring circuit 210 of the battery packs 10 a, 10 b, 10 c, and 10 ddescribed with reference to FIG. 2 to FIG. 5.

Referring to FIG. 21, the cell-balancing control circuit 500 a forperforming a cell-balancing method according to a fourth embodiment ofthe present disclosure may include a plurality of timers 501, 504, and508, a delay unit 502, a counter 503, a comparator 505, a balancingtrigger 507, and a balancing controller 509.

The timer 501 generates a timing signal with an execution cycle (e.g.,40 ms) of the cell-balancing task (Task).

The delay unit 502 delays the timing signal output by the timer 501 byan amount of time (e.g., a predetermined time), and transmits thedelayed timing signal to the counter 503. Accordingly, the timing signalgenerated by the timer 501 is transmitted to the counter 503 to generatea counting up of the counter 503.

The timer 504 generates a timing signal for each balancing cycle (e.g.,4 sec). The timing signal generated by the timer 504 is input to thecounter 503, and resets the counter 503.

Therefore, the counter 503, as shown in FIG. 21, increases a countervalue through a count up for each 40 ms that is an execution period ofthe cell-balancing task, and is reset for each 4 sec that is a balancingcycle.

The counter value generated by the counter 503 is transmitted to thecomparator 505.

The comparator 505 receives a counter value input by the counter 503,and receives a duty-setting value 506 of the corresponding balancingchannel, and outputs a comparison result of the two values. Here, theduty-setting value 506 is acquired from the duty cycle set for thecorresponding balancing channel, and corresponds to the number of timesof execution of the cell-balancing tasks for satisfying the duty cycleof the corresponding balancing channel.

That is, the duty-setting value corresponds to the number of executionsof the cell-balancing tasks by which the total time of balancingdischarging that is performed by a repetitive execution ofcell-balancing tasks becomes substantially identical to the totalduration of time that is set for the corresponding balancing channel.

When the counter value input by the counter 503 is less than theduty-setting value 506 of the corresponding balancing channel, thecomparator 505 enables the balancing trigger 507. Contrarily, when thecounter value input by the counter 503 is equal to or greater than theduty-setting value 506 of the corresponding balancing channel, thecomparator 505 disables the balancing trigger 507.

The balancing trigger 507 triggers the operation of the timer 508, andis enabled/disabled by the comparator 505. That is, the balancingtrigger 507 operates the timer 508 while being enabled by the comparator505.

The timer 508 is operated by the balancing trigger 507, and generates atiming signal for instructing a balancing discharge section (e.g., 15ms) within the execution cycle of the cell-balancing task.

The balancing controller 509 controls the operation (e.g., turn-on/off)of the corresponding balancing switch (SWb) according to the timingsignal output by the timer 508.

Referring to FIG. 22 and FIG. 23, the output counter 503 in the presentexample counts up the counter value for each 40 msec execution cycle ofthe cell-balancing task by the timer 501, and is reset for each 4 secbalancing cycle. The counter value is input to the comparator 505 and iscompared with the duty-setting value 506.

The comparator 505 enables the balancing trigger 507 when the countervalue is less than the duty-setting value 506. When the balancingtrigger 507 is enabled by the comparator 505, it operates the timer 508,and the balancing controller 509 turns on the balancing switch (SWb) for15 ms according to the timing signal generated by the operation of thetimer 508 such that balancing discharging is performed for 15 ms.

When the counter value is equal to or greater than the duty-settingvalue 506, the comparator 505 disables the balancing trigger 507, andthe timer 508 is also disabled and the balancing discharging is notperformed.

As described above, when the balancing discharging within one balancingcycle is processed by a repetitive execution of cell-balancing tasks,and when the balancing discharging progresses for part of the sectionwhile one cell-balancing task is performed, it is possible to performanother task, such as diagnosis, for the remaining section in which thebalancing discharging is not performed. Accordingly, it is possible tosimultaneously perform a cell-balancing task and another task.

The cell-balancing control circuit 500 a shown in FIG. 21 represents abalancing control circuit for one balancing channel, and when this isapplied to a plurality of balancing channels, they may configure acell-balancing control circuit 500 b as shown in FIG. 24.

FIG. 24 shows another example of a cell-balancing control circuit forperforming a cell-balancing method according to a fourth embodiment ofthe present disclosure shown in FIG. 20, in which three balancingchannels are shown as an example. FIG. 25 shows a balancing controltiming diagram using a cell-balancing control circuit of FIG. 24. Thecell-balancing control circuit 500 b shown in FIG. 24 may be included inthe battery monitoring circuit 210 of the battery packs 10 b, 10 c, and10 d described with reference to FIG. 3 to FIG. 5.

Referring to FIG. 24, the cell-balancing control circuit 500 b sharesthe timers 501 and 504, the delay unit 502, and the counter 503 relatingto the execution of cell-balancing tasks for all balancing channels. Thecomparators 505 a, 505 b, and 505 c, the balancing triggers 507 a, 507b, and 507 c, the timers 508 a, 508 b, and 508 c, and the balancingcontrollers 509 a, 509 b, and 509 c relating to execution of balancingdischarging for the respective balancing channels are independently usedfor the respective balancing channels.

The counter 503 counts up the counter value for each 40 msec executioncycle of cell-balancing tasks by the timer 501, and it is reset for each4 sec balancing cycle.

The counter values counted by the counter 503 are input to thecomparators 505 a, 505 b, and 505 c of the respective balancing channelsCH1, CH2, and CH3, and are compared with the corresponding duty-settingvalues 506 a, 506 b, and 506 c.

The comparators 505 a, 505 b, and 505 c enable the correspondingbalancing triggers 507 a, 507 b, and 507 c when the counter value isless than the corresponding duty-setting values 506 a, 506 b, and 506 c.When the balancing triggers 507 a, 507 b, and 507 c are enabled by thecomparators 505 a, 505 b, and 505 c, they operate the correspondingtimers 508 a, 508 b, and 508 c, and the balancing controllers 509 a, 509b, and 509 c of the corresponding balancing channel turn on thebalancing switch (SWb) for 15 ms according to the timing signalgenerated by the operation of the respective timers 508 a, 508 b, and508 c, such that the balancing discharging is performed for 15 ms.

When the counter value is equal to, or greater than, the correspondingduty-setting values 506 a, 506 b, and 506 c, the comparators 505 a, 505b, and 505 c disable the corresponding balancing triggers 507 a, 507 b,and 507 c to stop the balancing discharging of the correspondingbalancing channel.

The cell-balancing control circuit 500 b of FIG. 24, as shown in FIG.25, represents a cell-balancing control circuit for the case in whichthe balancing of the odd-numbered cell and the even-numbered cell may besimultaneously performed.

FIG. 26 shows another example of a cell-balancing control circuit forperforming a cell-balancing method according to a fourth embodiment ofthe present disclosure shown in FIG. 20, indicating a case in which abalancing of the odd-numbered cell and the even-numbered cell arealternately performed in a like manner of the battery pack 10 adescribed with reference to FIG. 2. FIG. 27 shows a balancing controltiming diagram using a cell-balancing control circuit of FIG. 26.

Referring to FIG. 26, the cell-balancing control circuit 500 c sharesthe timers 501 and 504, the delay unit 502, and the counter 503 relatingto the execution of cell-balancing tasks on the balancing channels, andthe comparators 505 d, 505 e, and 505 f, the balancing triggers 507 d,507 e, and 507 f, the timers 508 d, 508 e, and 508 f, and the balancingcontrollers 509 d, 509 e, and 509 f relating to the execution ofbalancing discharging of the respective balancing channels areindependently used for the respective balancing channels.

The counter 503 counts up the counter value for each 40 msec that is theexecution cycle of the cell-balancing task by the timer 501, and isreset for each 4 sec that is the balancing cycle.

The counter value counted by the counter 503 are input to thecomparators 505 d, 505 e, and 505 f of the balancing channels CH1, CH2,and CH3 and are compared to the duty-setting values 506 d, 506 e, and506 f. The duty-setting values 506 d, 506 e, and 506 f may be set to theodd-numbered channels CH1 and CH3 corresponding to the off duty (e.g.,calculated by 100%−ON Duty %) and may be set to the even-numberedchannel CH2 corresponding to the on duty (e.g., corresponding to theduration of the on duty).

Here, the duty-setting value 506 e corresponding to the “On” duty isobtained from the duty cycle set for the corresponding balancing channelCH2, and it corresponds to the number of separate cell-balancing tasksfor the “On” section of the corresponding balancing channel. Further,the duty-setting values 506 d and 506 f set corresponding to the “Off”duty is obtained from the duty cycle set for the corresponding balancingchannels CH1 and CH3, and corresponds to the execution number ofcell-balancing tasks for the “Off” section of the correspondingbalancing channel.

Accordingly, when the counter value is equal to or greater than theduty-setting values 506 d and 506 f set corresponding to the “Off” duty,the comparators 505 d and 505 f of the odd-numbered balancing channelsCH1 and CH3 enable the balancing triggers 507 d and 507 f. The timers508 d and 508 f are operated, and the balancing controllers 509 d and509 f of the corresponding balancing channels CH1 and CH5 turn on thebalancing switch (SWb) for 15 ms, so the balancing discharging isperformed for 15 ms.

Contrarily, when the counter value is less than the duty-setting values506 d and 506 f set corresponding to the “Off” duty, the comparators 505d and 505 f of the odd-numbered balancing channels CH1 and CH3 disablethe corresponding balancing triggers 507 a, 507 b, and 507 c to thusstop the balancing discharging of the corresponding balancing channelsCH1 and CH3.

When the counter value is equal to or greater than the duty-settingvalue 506 e set corresponding to the “Off” duty, the comparator 505 e ofthe even-numbered balancing channel CH2 enables the balancing trigger507 e. Accordingly, the timer 508 e is operated, and the balancingcontroller 509 e of the balancing channel CH2 turns on the balancingswitch (SWb) for 15 ms, so the balancing discharging is performed for 15ms.

Contrarily, when the counter value is less than the duty-setting value506 e set corresponding to the “Off” duty, the comparator 505 e of thebalancing channel CH2 disables the corresponding balancing trigger 507 eto stop the balancing discharging of the corresponding balancing channelCH2.

Accordingly, when the sum of the duty cycles of two adjacent cells isequal to or less than 100%, as shown in FIG. 27, it is possible tocontrol the balancing discharging of the odd-numbered cell and theeven-numbered cell to be not simultaneously performed. It is shown inFIG. 26 and FIG. 27 that the balancing discharging of the even-numberedcell within the balancing cycle is performed, and the balancingdischarging of the odd-numbered cell is then performed. It is alsopossible to allow the balancing discharging of the odd-numbered cellwithin the balancing cycle to be performed, and the balancingdischarging of the even-numbered cell to be then performed. In thiscase, the duty-setting value is set corresponding to the “Off” duty(e.g., calculated by 100%−ON Duty %) regarding the even-numberedchannel, and it may be set corresponding to the “On” duty (i.e.,duration) regarding the odd-numbered channel.

According to the above-described embodiments, the heat radiationperformance of the substrate may be maintained and the balancing timemay be reduced.

The accompanying drawings and the embodiments of the present disclosureare only examples of the present disclosure, and are used to describethe present disclosure but do not limit the scope of the presentdisclosure as defined by the following claims. It will be understood bythose of ordinary skill in the art that various modifications andequivalent embodiments may be made. Therefore, the technical scope ofthe present disclosure may be defined by the technical idea of thefollowing clams, with functional equivalents thereof to be includedherein.

What is claimed is:
 1. A battery management system comprising: aplurality of balancing resistors respectively forming balancingdischarging paths of cells connected in series to each other; aplurality of balancing switches respectively connected between the cellsand the balancing resistors, and configured to control cell-balancing ofeach of the cells; a voltage-detecting circuit for detecting respectivecell voltages of the cells; and a battery controller for acquiringrespective balancing capacities of the cells based on the cell voltages,for obtaining duty cycles of the balancing switches according to thebalancing capacities, and for scaling the duty cycles of the balancingswitches according to a sum of duty cycles of two adjacent cells fromamong the cells.
 2. The battery management system of claim 1, whereinthe two adjacent cells partly share a balancing discharging path forcell-balancing.
 3. The battery management system of claim 2, whereinbalancing switches of the two adjacent cells are alternately turned on.4. The battery management system of claim 1, wherein the batterycontroller is configured to calculate a sum of duty cycles ofcombination of two adjacent cells, is configured to calculate a scalefactor so that a maximum value of the sum of duty cycles is 100%, and isconfigured to scale the duty cycles of the balancing switches using thescale factor.
 5. The battery management system of claim 1, wherein thebattery controller is configured to set a ratio of respective dutycycles of the balancing switches based on a ratio of respectivebalancing capacities of the cells.
 6. The battery management system ofclaim 1, further comprising a battery integrated circuit for controllingthe balancing switches according to the duty cycles of the balancingswitches.
 7. A battery management system comprising: a plurality ofbalancing resistors respectively forming balancing discharging paths ofcells connected in series to each other; a plurality of balancingswitches respectively connected between the cells and the balancingresistors for controlling a cell-balancing of each of the cells; avoltage-detecting circuit for detecting cell voltages of the cells; anda battery controller for acquiring balancing capacities of the cellsbased on the cell voltages, for obtaining duty cycles of the pluralityof balancing switches according to the balancing capacities, and forscaling the duty cycles of the plurality of balancing switches accordingto a power consumption upper limit corresponding to a balancingdischarging of the cells.
 8. The battery management system of claim 7,wherein the battery controller is configured to calculate a total powerconsumption by summing the balancing capacities of the cells, and isconfigured to scale the duty cycles of the balancing switches when thetotal power consumption is greater than the power consumption upperlimit.
 9. The battery management system of claim 8, wherein the batterycontroller sets a ratio of respective duty cycles of the balancingswitches based on a ratio of respective balancing capacities of thecells.
 10. The battery management system of claim 7, wherein the batterycontroller is configured to calculate a current scale factor based on aratio of a current upper limit on a substrate on which the balancingresistors are mounted to a sum of average balancing currents flowing ineach of the balancing discharging paths, and is configured to scale theduty cycles of the balancing switches by using the current scale factor.11. The battery management system of claim 7, wherein the batterycontroller is configured to scale the duty cycles of the balancingswitches according to a current upper limit allowable to a singlebalancing discharging path.
 12. The battery management system of claim7, wherein the battery controller is configured to calculate a currentscale factor of each of the balancing switches based on a ratio of acurrent upper limit to an average balancing current flowing in each ofthe balancing discharging paths, and is configured to scale the dutycycles of the balancing switches by using the current scale factor. 13.The battery management system of claim 7, wherein the battery controlleris configured to scale the duty cycles of the balancing switchesaccording to a sum of duty cycles between two adjacent cells from amongthe cells.
 14. A battery management system comprising: a plurality ofbalancing resistors respectively forming balancing discharging paths ofcells connected in series to each other; a plurality of balancingswitches respectively connected between the cells and the balancingresistors for controlling a cell-balancing of each of the cells; avoltage-detecting circuit for detecting cell voltages of the cells; abattery controller for acquiring balancing capacities of the cells basedon the cell voltage, and for obtaining duty cycles of the balancingswitches according to the balancing capacities; and a battery integratedcircuit for controlling operation of the balancing switches by using abalancing task, which is repeatedly executed during an execution cyclethat is shorter than a balancing cycle, and which corresponds to theduty cycles, to allow a turn-on state of the balancing switches onlyduring a part of an execution period of the balancing task.
 15. Thebattery management system of claim 14, wherein the battery integratedcircuit is configured to count on-periods, in which the balancingswitches are turned on by the balancing task within one balancing cycle,for each of the balancing switches, and is configured to maintain astate of a balancing switch in a turn-off state until the balancingcycle ends wherein a value obtained by counting on-periods correspondsto a duration of a corresponding duty cycle.
 16. The battery managementsystem of claim 14, wherein the battery controller sets a ratio ofrespective duty cycles of the balancing switches based on a ratio ofrespective balancing capacities of the cells.
 17. The battery managementsystem of claim 16, wherein the battery controller is configured toscale the duty cycles of the balancing switches according to a sum ofduty cycles between two adjacent cells from among the cells.
 18. Thebattery management system of claim 16, wherein the battery controller isconfigured to scale the duty cycles of the balancing switches accordingto a power consumption upper limit of the cells.
 19. The batterymanagement system of claim 16, wherein the battery controller isconfigured to scale duty cycles of the balancing switches according to acurrent upper limit of a single balancing discharging path.
 20. Acell-balancing method of a battery pack comprising a plurality of cellsconnected in series to each other, the method comprising: detecting cellvoltages of the cells; acquiring balancing capacities of the cells basedon the cell voltages; acquiring duty cycles of a plurality of balancingswitches for controlling a balancing discharging of the cells based onone or more respective ratios of the balancing capacities of the cells;and controlling the balancing switches based on the duty cycles.
 21. Thecell-balancing method of claim 20, further comprising scaling the dutycycles of the balancing switches according to a sum of duty cyclesbetween two adjacent cells from among the cells.
 22. The cell-balancingmethod of claim 20, further comprising scaling the duty cycles of thebalancing switches according to a power consumption upper limit of abalancing discharging of the cells.
 23. The cell-balancing method ofclaim 20, further comprising scaling the duty cycles of the balancingswitches according to a current upper limit of one of balancingdischarging paths of the cells.
 24. The cell-balancing method of claim20, wherein the controlling comprises: repeatedly performing a balancingtask having an execution cycle that is shorter than a balancing cyclecorresponding to the duty cycle, and allowing a turn-on state of thebalancing switches only during a part of an execution period of thebalancing task; counting periods in which the balancing switches areturned on by the balancing task within one balancing cycle for each ofthe balancing switches; and maintaining a state of a balancing switch ina turn-off state until the balancing cycle ends, wherein a valueobtained by counting periods in which the balancing switches are turnedon by the balancing task satisfies a duration of a corresponding dutycycle.